Modelisation des erreurs geometriques et dynamiques pour predire et compenser les erreurs volumetriques des machines-outils a cinq axes (application fraisage orbital)

Five axis machine tools are important in modern production systems. The dynamics of axes and the complex structures of the machines produce inaccuracies of positioning at the tool tip that influence the quality of machined parts, the propagation of geometric and dynamic errors forming the principal volumetric error sources in the workspace. To improve the accuracy of machine tools, these errors must be defined, modeled mathematically, predicted and compensated.;First, joint motion errors of prismatic axis for a five axes machine tool are measured experimentally using a laser interferometer and a mathematical model is proposed to represent these errors. The hysteresis is significant and hence is included in the model. Since the hysteresis occurs when the direction of approach is reversed, measurements are made bidirectional.;The second source of errors is dynamics. A second order transfer function model is proposed to predict the dynamic error for each axis. The effect of the squareness and scale errors are also added to the model. To estimate the parameters of the model, a series of tests with different radius and feedrates are conducted using the KGM grid encoder. Subsequently, a compensation strategy is proposed to improve the accuracy of the machine tool during high speed end mill boring.;A method to assess, model and predict the volumetric errors at different feedrates for XYC circular paths is proposed. Two measurement techniques are used. The first is based on a 3D measurement instrument capable of measuring the volumetric positioning errors between a point attached to the tool reference frame and another fixed to the machine table reference frame. The second technique relies on measuring the dynamic error by collecting the position feedback signal from the encoder provided by the machine controller. Based on the measurements obtained from the 3D measurement system at feedrate of 500 mm/min, the parameters of the geometric error model including hysteresis have been estimated. The parameters estimated and the measured dynamic errors are used to predict the volumetric errors at selected feedrate.;This thesis aims to achieve three objectives. The first is to model the geometric and dynamic errors of a five axis machine tool. The second objective is to predict the 3D volumetric errors. The third objective is to improve the machine accuracy by compensation for these errors.;Finally, a concept for geometries and dynamics errors integration is proposed for five axes machines tools. The validity of the concept is tested experimentally in XYC circular paths.